Project Summary Arsenic exposure is associated with various acute and chronic health effects. The World Health Organization (WHO) estimates that over 200 million people worldwide are chronically exposed to arsenic in drinking water at concentrations above the WHO safety standard. Emerging evidence from epidemiological studies in multiple countries indicate a strong link between environmental arsenic exposure and increased incidence of anemia, suggesting that arsenic is a human hematotoxicant. However, little is known about how arsenic causes hematotoxicity and how this adverse effect of arsenic can be prevented. Research from our labs demonstrates that: i) Analysis of blood collected from a group of people in Bangladesh exposed to a wide range of arsenic in their drinking water revealed positive effects of arsenic exposure on hematological indicators of anemia; ii) Hematology analysis of blood from mice treated 60 days via drinking water with environmentally relevant concentrations of sodium arsenite (As+3) showed significant alterations in measures of hemoglobin as well as impaired bone marrow erythropoiesis; iii) More intriguingly, our preliminary study revealed that GATA-1, a key transcription factor that mediates both the development and function of red blood cells, is a sensitive molecular target for arsenic interaction. We found that As+3 could replace zinc in the zinc finger moiety of GATA-1 at low non-cytotoxic concentrations, resulting in loss of zinc and protein function. Based on our compelling experimental evidence, we hypothesize that exposure to environmentally relevant concentrations of arsenic causes anemia through inhibiting GATA-1 function by disrupting its zinc finger domain. In Aim 1, we will utilize a variety of cell biology and biochemical methods to definitively examine the impact of As+3 exposure on the process of red blood cell production. These findings will establish what specific steps in the lineage of RBC production that arsenic exposure affects, and how arsenic interrupts these steps. Aim 2 will investigate As+3 interaction with GATA-1 and the functional consequences of this interaction. The experiments are designed to reveal the specific mechanisms by which As+3 interacts with GATA-1 to disrupt its function in cells. In Aim 3, we will validate GATA-1 as a sensitive target in vivo, and test the hypothesis that zinc supplement can prevent arsenic-induced hematotoxicity. The outcomes from our vigorously designed studies are expected to provide novel insights in our understanding of mechanisms underlying increased incidents of anemia in populations exposed to arsenic, thus filling a critical gap in our knowledge of arsenic-induced anemia. Importantly, our study will provide a solid foundation for a clear mechanistic understanding of how supplemental zinc reduces arsenic-induced anemia, and provide the proof of principle for the potential of zinc supplements to prevent arsenic-induced anemia. If validated, supplemental zinc could represent a low cost and easily implemented strategy to prevent anima in arsenic exposed populations.